Copending U.S. patent application Ser. No. 785,669, filed Apr. 7, 1977, incorporated herein by reference, describes the use of water-immiscible solutions alkyl aromatic sulfonic acids, particularly didodecylnaphthalene sulfonic acid, alone or in combination with an .alpha.-hydroxy oxime, as solvent-extractants for metal values in aqueous media.
Gallacher, U.S. Pat. No. 4,018,865, also incorporated herein by reference, describes the separation of difficult to separate metal value pairs using an alkylaromatic sulfonic acid and an .alpha.-hydroxy oxime in a water immiscible liquid as a superior solvent-extractant.
It has now been discovered that the selective extraction efficiency of the foregoing solvent-extractants comprising an alkyl aromatic sulfonic acid, alone, or combined with an .alpha.-hydroxy oxime, can be vastly improved by the addition of a fuzed ring aromatic N-alkyl triazole. Four significant effects have been observed following the addition of the triazole to the solvent-extractant: (i) faster extraction kinetics; (ii) improved selectively as between components in the metal pairs; (iii) increased extraction of the first metal value in the pair; and (iv) improved chemical stability of the extractant when in contact with typical stripping acids. These advantages will become apparent from the Examples hereinafter set forth.